Device including at least one seal in the form of a rolling diaphragm between two co-axially arranged relatively movable elements



Sept- 5, 1967 J. A. RIETDIJK 3, 3

DEVICE INCLUDING AT LEAST ONE SEAL IN THE FORM OF A ROLLING DIAPHRAGM BETWEEN TWO CO-AXIALLY ARRANGED RELATIVELY MOVABLE ELEMENTS Filed Dec. 5. 1964 2 Sheets-Sheet l d1 2 2. I E! INVENTOR JOHAN A. RIETDIJK AGENT Sept. 5, 1967 J. A. RIETDIJK 3,339,464

DEVICE INCLUDING AT LEAST ONE] SEAL IN THE FORM OF A ROLLING DIAPHRAGM BETWEEN TWO CO-AXIALLY ARRANGED RELATIVELY MOVABLE ELEMENTS Fil ed Dec. 5? 1964 2 Sheets-Sheet 2 7 2 17 M A r 55. /18

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AGENT ice Patented Sept. 5, 1967 3,339,464 DEVICE INCLUDING AT LEAST ONE SEAL IN THE FORM OF A ROLLING DIAPHRAGM BE- TWEEN TWO CO-AXIALLY ARRANGED REL- ATIVELY MOVABLE ELEMENTS Johan Adriaan Rietdijk, Emmasingel, Eindhoven, Netherlands, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Dec. 3, 1964, Ser. No. 415,711 Claims priority, application Netherlands, Dec. 13, 1963, 301,824 3 Claims. (Cl. 92-98) This invention relates to a device including at least one seal in the form of a rolling diaphragm between two co-axially arranged, relatively movable elements, each rolling diaphragm separating two spaces each containing a medium, the medium contained in one of the said spaces being substantially uncompressible, and means being provided for maintaining a pressure difference across each rolling diaphragm which is substantially constant at least during each stroke.

Known devices of the kind to which the present invention relates are, for example, compressors, cold-gas refrigerators, hot-gas engines, etc. In such devices the rolling diaphragm completely seals a working space. However, the said known devices have the disadvantage that the material of the rolling diaphragm exhibits creep by the action of the pressure difference prevailing over it, that is to say the rolling diaphragm becomes longer in course of time and hence thinner. In known devices the walls of the gap housing the rolling diaphragm are made parallel to one another. This implies that the surface area of the diaphragm across which the pressure difference prevails is invariably the same independently of the degree of extension of the rolling diaphragm, Consequently the total force to be absorbed by the rolling diaphragm is also invariably the same. If the rolling diaphragm becomes thinner through creep the tension in the rolling diaphragm will therefore increase. We are thus concerned as it were with an avalanche effect and the creeping velocity will increase more and more.

The present invention is based on recognition of the fact that the accelerated creep may be counteracted by providing that the tension in the rolling diaphragm upon creeping increases less rapidly or not at all. I 1

To realize this recognition, the device according to the invention is characterized in that the wall parts of the relatively movable elements which form the gap containing the rolling diaphragm, at least from the area where the rolling diaphragm is secured to the wall parts, are relatively convergent towards the space to which the convex side of the rolling diaphragm is adjacent.

If the rolling diaphragm becomes longer and thinner through creep, the surface area of the rolling diaphragm across which the pressure difierence prevails also becomes smaller. Consequently the total force to be absorbed by the rolling diaphragm also becomes smaller and hence the tension in the rolling diaphragm will substantially not vary. The tendency for the rolling diaphragm seal to become elongated has been overcome by a surprisingly simple construction.

The convergent Wall parts are not bound to a determined geometric shape, the only condition being that the .gap becomes narrower.

In one advantageous embodiment of the device according to the invention the convergent wall parts have a conical shape, the conical gap formed between the said wall parts becoming narrower from the area where the rolling diaphragm is secured to the said wall parts towards the space to which the convex side of the rolling diaphragm is adjacent.

The conical wall parts have the advantage that they can be manufactured fairly easily.

In another advantageous embodiment of the device according to the invention the conical wall parts are formed 5 as parts of peripheral surfaces of cones having the same apical angle.

Another advantageous embodiment of the device according to the invention is characterized in that the convergent wall parts extend so that the quotient d/s has the same value for any length of the rolling diaphragm, d being the thickness of the rolling diaphragm in the portion thereof which does not engage the wall parts and s being the width of the gap at the area where the rolling diaphragm disengages 'from the Wall parts.

This embodiment afiords the advantage that the tension in the rolling diaphragm invariably has the same value. Acceleration of the creep is thus completely avoided and this naturally has a favourable influence on the lift of the rolling diaphragm.

According to the invention a device comprising two rolling diaphragms as seals which are arranged between the adjacent walls of the movable elements and the convex or concave sides of which are adjacent one another, wherein the space between the said rolling diaphragms also contains an uncompressible medium, is characterized in that the wall parts with which one rolling diaphragm co-acts and the wall parts with which the other rolling diaphragm co-acts are convergent in opposite directions.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, showing several cylinder-piston com binations provided with seals in the form of rolling diaphragms.

FIG. 1 shows a known device in which the rolling diaphragm is arranged in a gap the walls of which areparallel to one another;

FIGURES 2 and 3 are sectional views of two devices in which the rollin diaphragms are arranged in gaps which become narrower;

FIG. 4 shows a device in which two rolling diaphragms are arranged as seals between a piston and its cylinder;

, FIG. 5 shows a device in which the rolling diaphragm is arranged in a gap the walls of which are convergent along curved lines.

Referring now to FIGURE 1, the reference numeral 1 indicates a cylinder in which two pistons 2 and 3 are movable. Between the pistons 2 and 3 is a space 4 filled with liquid. The piston 3 has a piston rod 5 which in turn may be connected to a driving mechanism (not shown). A line 6 for the supply of liquid is connected to the space 4. The upper side of the piston 2 can vary the volume of a working space 7. The lower side of the piston 2 is provided with a control pin 8 which exhibits a rim of orifices 9. A spring 10 ensures that the pressure in the liquid in space 4 is invariably lower than the pressure in the space 7. If an excessive amount of liquid is supplied through line 6 so that the pressure difference would become smaller than the pressure difference desired, the distance between the pistons 2 and 3 becomes a little greater and the orifices 9 come free so that liquid can flow from the space 4 to the crank case.

A rolling diaphragm 11 is arranged as a seal between the piston 2 and the cylinder 1 so that the pressure difference Ap caused by spring 10 prevails across the said rolling diaphragm. As a result of this pressure difference the material of the rolling diaphragm has a tendency to creep. The figure shows the initial position of the rolling diaphragm in full lines. In this position the rolling diaphragm has a thickness d The width of the gap is indicated by S. When viewed in an axial section, the

The tension has thus increased which means that creeping will proceed more and more rapidly.

To avoid this increase in creeping velocity, the rolling diaphragms in FIGURES 2 to are arranged in gaps which become narrower. In these figures the same reference numerals are used as in FIGURE 1.

FIGURE 2 shows a device which, as previously stated, comprises the same components as the device of FIG- URE 1. The only difierence is that the wall parts 12 and 13 of the cylinder 1 and the piston 2 respectively, are not now parallel to one another but convergent. The operation of the device is otherwise exactly the same as that of the device of FGURE 1. Thus again the pressure difference Ap prevails across the rolling diaphragm 11. The initial position of the rolling diaphragm is again shown in full line. The thickness of the rolling diaphragm in this position is again d and the width of gap at the area where the rolling diaphragm 11 disengages from the wall parts 12 and 13 is indicated by S As viewed in axial section, the rolling diaphragm is thus subjected to a force K =S.Ap. The tension in the rolling diaphragm is thus After some time the rolling diaphragm, due to the creep occurring, has reached a position as shown in broken lines in FGURE 2. The thickness of the rolling diaphragm is now d which is less than d. The width of gap at the area where the rolling diaphragm 11 disengages from the wall parts 12 and 13 is now S which is less than S The force acting on the rolling diaphragm is now K =S Ap. The tension in the rolling diaphragm is thus K /2a Since now both d and K are less than d and K the tension F can be equal to the tension F This is the case if Consequently the creeping velocity will not increase. It iseven possible to make the wall parts 12 and 13 convergent to one another so greatly that the tension F is less than the tension F so that the creeping velocity will be reduced.

The said conical gap has the additional advantage that the rolling diaphragm also becomes less sensitive to variations in the pressure difference.

FIGURE 3 shows a device identical to that of FIG- URES 1 and 2 but with the convex side of the rolling diaphragm 11 adjacent to the working space 7. The gap between the wall parts 12 and 13 now becomes narrower towards the working space 7. In this position of the rolling diaphragm 11 the spring 10 has to be formed as a pull spring so that the pressure in the liquid in the space 4 exceeds that in the working space 7. The operation of the device is otherwise similar to that of the device of FIGURE 2.

FIGURE 4 again shows a device the main components of which correspond to those of the devices of FIGURES 2 and 3. The seal between the piston 2 and the cylinder 1 is now constituted by two rolling diaphragms 14 and 15 the concave sides of which are adjacent to one another. A space 16 between the rolling diaphragms is filled with an amount of liquid such that the pressure prevailing in the said space is higher by a constant amount than the pressure in the working space 7 and in the space 4. In order to maintain the creeping velocity of the rolling diaphragms within permissible limits, both rolling diaphragms co-act with convergent wall parts, the gap between the wall parts 17 and 18 with which the rolling diaphragm 14 co-acts becoming narrower in a direction opposite to the direction in which the wall parts 19 and 20 with which the rolling diaphragm 15 co-acts are convergent.

The piston-cylinder combination as shown lends itself especially for use in compressors, cold-gas refrigerators, hot-gas engines, expansion machines, etc.

The drawings show only a few examples of rolling diaphragms. Although in the figures both the wall part of the piston and that of the cylinder are made sloping, it will be evident that it is also possible to make one of the said wall parts cylindrical and the other sloping. It will be evident that the principle underlying the invention is also applicable to other structures of rolling diaphragms which are not shown.

Lastly, FIGURE 5 shows a seal in the form of a rolling diaphragm the wall parts 12 and 13 of which are not rectilinear. In this construction, too, the occurrence of accelerated creep is prevented due to the gap between the wall parts 12 and 13 becoming narrower. From this it appears that, although the conical shape affords certain advantages in manufacture, wall parts of a different shape can also be used.

What is claimed is:

1. An apparatus comprising a cylinder, at least one reciprocable piston in said cylinder, a rolling diaphragm seal connected to said piston and said cylinder and defining two separate spaces, one of said spaces containing an incompressible liquid column, means being provided for maintaining a pressure difference across said rolling diaphragm seal which is substantially constant during each stroke of said piston, the adjacent walls of said piston and cylinder which form the gap containing said rolling diaphragm seal being convergent with respect to one another towards the space to which the convex side of said rolling diaphragm seal is adjacent, said rolling diaphragm seal assuming the configuration of said converging walls, said convergent walls extending so that the quotient d/s has the same value for any length of said rolling diaphragm seal, d being the thickness of said rolling diaphragm seal in the part thereof which does not engage said convergent walls, and s being the width of the gap at the location where the rolling diaphragm seal disengages from said walls.

2. An apparatus as claimed in claim 1 wherein said convergent walls are curvilinear.

3. An apparatus comprising a cylinder, at least one reciprocable piston in said cylinder, a first rolling diaphragm seal connected to said piston and said cylinder and defining two separate spaces, one of said spaces containing an incompressible liquid column, means being provided for maintaining a pressure difference across said rolling diaphragm seal which is substantially constant during each stroke of said piston, the adjacent walls of said piston and cylinder which form the gap containing said rolling diaphragm seal being convergent with respect to one another towards the space to which the convex side of said rolling diaphragm seal is adjacent, said rolling diaphragm seal assuming the configuration of said converging walls, a second rolling diaphragm seal connected to said piston and cylinder, both of said seals being V-shaped and engaging each other and extending in 0pposite directions, a space formed between said two rolling diaphragm seals having an incompressible liquid me dium therein, and the Wall parts for one of said rolling diaphragm seals being convergent in opposite directions to the wall parts for the other of said rolling diaphragm seals.

6 References Cited UNITED STATES PATENTS 971,583 11/1910 Bell 267-65 5 3,277,795 10/1966 Rietdijk 9284 FOREIGN PATENTS 122,068 3/1961 Austria.

EDGAR W. GEOGHEGAN, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

G. N. BAUM, Assistant Examiner. 

1. AN APPARATUS COMPRISING A CYLINDER, AT LEAST ONE RECIPROCABLE PISTON IN SAID CYLINDER, A ROLLING DIAPHRAGM SEAL CONNECTED TO SAID PISTON AND SAID CYLINDER AND DEFINING TWO SEPARATE SPACES, ONE OF SAID SPACES CONTAINING AN INCOMPRESSIBLE LIQUID COLUMN, MEANS BEING PROVIDED FOR MAINTAINING A PRESSURE DIFFERENCE ACROSS SAID ROLLING DIAPHRAGM SEAL WHICH IS SUBSTANTIALLY CONSTANT DURING EACH STROKE OF SAID PISTON, THE ADJACENT WALLS OF SAID PISTON AND CYLINDER WHICH FORM THE GAP CONTAINING SAID ROLLING DIAPHRAGM SEAL BEING CONVERGENT WITH RESPECT TO ONE ANOTHER TOWARDS THE SPACE TO WHICH THE CONVEX SIDE OF SAID ROLLING DIAPHRAGM SEAL IS ADJACENT, SAID ROLLING DIAPHRAGM SEAL ASSUMING THE CONFIGURATION OF SAID CONVERGING WALLS, SAID CONVERGENT WALLS EXTENDING SO THAT THE QUOTIENT D/S HAS THE SAME VALUE FOR ANY LENGTH OF SAID ROLLING DIAPHRAGM SEAL, D BEING THE THICKNESS OF SAID ROLLING DIAPHRAGM SEAL IN THE PART THEREOF WHICH DOES NOT ENGAGE SAID CONVERGENT WALLS, AND S BEING THE WIDTH OF THE GAP AT THE LOCATION WHERE THE ROLLING DIAPHRAGM SEAL DISENGAGES FROM SAID WALLS. 